1. Field of the Invention
The present invention relates to a modified sheet of material which may be used in connection with biochemical procedures, and more particularly, may be used as part of a separation technique in which substances of interest preferentially adhere onto the sheet material. The invention further relates to a method of making the sheet material and a method of using the sheet material as part of a biochemical procedure.
2. Description of Prior Art
Most biologically significant substances show a high affinity to specific ligands. For purposes of this invention, a ligand may be defined as any compound capable of recognizing another molecule. Ligands may include the substrate of an enzyme-substrate reaction; the enzyme template in more complicated processes of transcription and replication; the site of activity for bio-molecules having a tissue specificity, e.g., opiates for nerve cells; the complementary sequence in the case of nucleic acids; or antibodies in the case of antigens. In some instances, high affinity is not linked to a clear function such as, for example, in the specific binding of some nuclear and cytoplasmic proteins to the poly A end eukaryotic mRNA. Such affinities have been used for identification of the presence of such complement molecules as, for instance, in the isolation of antibodies by immobilizing antigens onto an agarose column (affinity chromatography); isolation of enzymes by immbolizing their substrate onto a mesh of polysaccharides, purification of poly A-rich RNA by immobilization of oligo dT or oligo U on a cellulose column; etc. All such techniques which have allowed for the identification of the presence of such a complementarity have not, however, allowed for the separation of the substance. This separation had to be performed separately by lengthy and often tedious techniques. Prior techniques also did not allow for the rapid screening of multiple samples since each sample in, for example, affinity chromatography, had to be analyzed on a separate column, be eluted and only then processed further.
Another problem with prior techniques was that when more than one component in a mixture is an active ligand, as, for example, in multiple immunoglobulin classes for a given antigen, the mixture of immunoglobulins stayed on the column and the actual assay of the different elements must be performed in a separate experiment for each sample.
Also, in the case of monoclonal antibody isolation, where hundreds of cell stains must be screened, the process was tedious and expensive.
In the pharmaceutical area, such as, for example, with drugs having receptors at nerve cell loci, where one was attempting to locate the receptors, the number of elements present rendered the task very difficult. Thus, the technique required that the active substance and the receptors being sought were determined only by a series of lengthy separation procedures, including gel electrophoresis, etc.
In view of the cumbersome and complicated nature of prior techniques, there is a strong demand for a technique by which specific interactions could be used at the same time to identify, as well as to separate and biologically purify relevant substances.
The Prior Art highlights this very problem. Chemical Abstract 90:18444r is an abstract of an article entitled A NEW METHOD FOR THE PREPARATION OF DNA CELLULOSE, by Bragioni et al., Anal Biochem, 1978, 89(2), 616-19, which discloses the use of cellulose which has been activated by cyanuric chloride (I). The abstract states that DNA binds in satisfactory amounts to the treated cellulose. Such a system is unsatisfactory since a subsequent elution step is necessary before the separated material can be processed.
It would, therefore, be advantageous if a technique were available and could be used both for locating material of interest as well as automatically separating it and making it available for subsequent processing.